Apart from being so far the only known binary multiferroic compound, CuO has a much higher transition temperature into the multiferroic state, 230 K, than any other known material in which the electric polarization is induced by spontaneous magnetic order, typically lower than 100 K. Although the magnetically induced ferroelectricity of CuO is firmly established, no magnetoelectric effect has been observed so far as direct crosstalk between bulk magnetization and electric polarization counterparts. Here we demonstrate that high magnetic fields of ≈ 50 T are able to suppress the helical modulation of the spins in the multiferroic phase and dramatically affect the electric polarization. Furthermore, just below the spontaneous transition from commensurate (paraelectric) to incommensurate (ferroelectric) structures at 213 K, even modest magnetic fields induce a transition into the incommensurate structure and then suppress it at higher field. Thus, remarkable hidden magnetoelectric features are uncovered, establishing CuO as prototype multiferroic with abundance of competitive magnetic interactions.

中文翻译：

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CuO在外部磁场中的磁电效应和相变。

除了到目前为止是唯一已知的二元多铁化合物之外，CuO到多铁态的转变温度要高得多，为230 K，比任何其他通过自发磁序感应极化的其他已知材料（通常低于100 K）高。尽管已牢固地建立了CuO的磁感应铁电性，但在体磁化和极化极化之间存在直接串扰的情况下，尚未观察到磁电效应。在这里，我们证明了≈50 T的高磁场能够抑制多铁性相中自旋的螺旋调制并极大地影响电极化。此外，正好在213 K从自相称（顺电）结构向不相称（铁电）结构的自发转变以下，即使是适度的磁场也会导致过渡到不相称的结构，然后在较高的磁场处将其抑制。因此，发现了显着的隐藏磁电特征，从而使CuO成为具有丰富竞争性磁相互作用的原型多铁性体。